The purpose of this work is fabrication of 3D structures consist of Zinc
Oxide (ZnO) nanorods. These devices would be employed for gas sensing at room
temperature due to the potential increase in active surface area. There were results
from research which have revealed that surfaces, covered by ZnO semiconductor,
present sensing behavior. Also, there have been work in construction of 3D arrays
of ZnO nanorods in the past but only its photocatalytic performance was
investigated. That is why 3D scaffolds were fabricated in order to serving us
substrates for growth of ZnO nanorods and examine the sensing behavior of ZnO
on complex geometries. The aim is to increase of sensing behavior this
semiconductor exhibits by increasing the surface area through which the
semiconductor interacts with the environment.
For the accomplishment of this work three main methods have been
adopted. Firstly, the 3D scaffolds were constructed using Multiphoton Lithography
(MPL) technique and the next step was deposition of seed Zn layer utilizing Pulsed
Laser Deposition (PLD) technique. Finally, hydrothermal growth of ZnO nanorods
was achieved by Aqueous Chemical Growth (ACG) technique. MPL is a direct
laser writing technique for fabrication of 3D scaffolds with features on submicron
scale with great accuracy. The idea is that phase transition from gel state to solid
state can be occurred via multiphoton polymerization of photosensitive materials.
After a special treatment, only the light exposed material can be remained with the
final result the desire 3D structures. PLD is a physical vapor deposition procedure
for thin films growth. It is a light-induced process in which stoichiometric transfer
is achieved through vaporization of a material. Only requirements are a bulk target
material, a substrate, a pulsed laser source and vacuum conditions and a pure layer
of desired material can be deposited into a substrate. The role of seed Zn layer from
PLD is crucial for uniformly growth of nanorods on substrates. ACG is a solution
growth technique, which is a quite simple method for growth of nanostructures. It
is taken place at relatively low temperatures, presenting several advantages such as
the use of non-expensive equipment, the requirement of cheap and non-toxic
reagents and the presence of non-hazardous by-products.